H. Krawczyk, Ł. Albrecht, J. Wojciechowski
Jul 1, 2006
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Acta Crystallographica Section E-structure Reports Online
Abstract
We have recently demonstrated that primary and secondary 3aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids undergo spontaneous Nef reactions (Ballini & Petrini, 2004) leading to 3-(diethoxyphosphoryl)-1-hydroxysuccinimides and 2-(diethoxyphosphoryl)-4-oxoalkanoic acids (Krawczyk et al., 2002; Krawczyk & Albrecht, 2005; Krawczyk et al., 2006). The title compound, (I), was prepared as a single diastereoisomer and is a key substrate in this reaction. Its relative stereochemistry at all three stereogenic centers C5, C11 and C12 is 2R*,3R*,4R*, respectively (Fig. 1). The molecule adopts an extended conformation with the phosphoryl and 4-nitrophenyl groups placed in antiperiplanar positions. The latter group is gauche with respect to the methyl substituent. The main bond lengths are close to those observed in related compounds (Cambridge Structural Database, Version 5.27, April 2006 update; ConQuest, Version 1.8; Mogul, Version 1.1; Allen, 2002) In particular, the N1—C12 bond is much longer [1.509 (4) Å] than the N2—C17 bond [1.460 (4) Å]; the standard values (Allen et al., 1992) are 1.509 and 1.468 Å, respectively. The shortening of C—C and C—O bonds in the diethoxphosphoryl groups (Table 1) has been observed in the crystal structures of organophosphorus compounds and may follow from high displacement parameters of the terminal C atoms. The latter are often prone to dynamic disorder (Wojciechowski & Wolf, 2006). However, an attempt to refine the C1/C2 ethyl group using a two-site disorder model gave unsatisfactory results.